The present invention is an Aircraft Takeoff and Abort Instrument utilizing a shifting liquid to indicate when the aircraft is achieving optimal linear acceleration during takeoff, or insufficient acceleration to make a safe takeoff.
A safe takeoff requires that the aircraft achieve adequate net thrust to produce proper acceleration. Many of the factors that reduce net thrust may not be noticed, or properly evaluated by the pilot. These include reduced engine thrust caused by malfunctions not shown by the engine instruments, increased drag caused by too much water or slush on the runway, flaps that have been lowered too far as a result of a malfunction or crew error, insufficient tire pressure, dragging brakes, or malfunctioning thrust reversers giving partial or full reverse thrust.
Should any of these things occur, the pilot may not realize that the aircraft is not accelerating properly, so he will continue the takeoff, fully expecting to accelerate to takeoff speed before running past a safe abort point, or out of runway. This is especially critical during conditions of poor visibility, which reduces the pilot's ability to judge his safe progress down the runway.
In view of these problems, various systems have been developed for automatically indicating whether and when to abort a takeoff. These systems typically rely on measuring either the air speed or the ground speed of the aircraft. If the speed is insufficient by the time the aircraft reaches the abort point for a particular set of conditions, the system activates a warning indicator.
Other systems for determining when to abort an aircraft during takeoff may be seen in U.S. Pat. No. 3,865,071 to Manor, which includes an electrical accelerometer interfaced to a display and uses a computer to compute various conditions of the takeoff. In the Hoekstra U.S. Pat. Nos. 2,922,982 and 3,174,710, an air speed indicator is coupled to a mechanically actuated indicator U.S. Pat. No. 4,284,029 to Roberts is for a takeoff safety indicator for aircraft having a double movement meter with crossover points to indicate takeoff conditions. U.S. Pat. No. 3,168,827 to Bailey uses a shifting mass connected to a linkage for driving a meter and includes adjustment for the aircraft load and the altitude of the runway, as well as for the temperature at the runway. U.S. Pat. No. 3,738,165 to Hanson shows an aircraft takeoff abort indicator which utilizes a shifting mass attached to a pendulum.
The present invention, on the other hand, is an aircraft takeoff and abort linear acceleration measuring instrument utilizing a shifting liquid in a closed tube that is dependent only upon the force of inertia for its proper function. Because of being completely self-contained, this instrument cannot be adversely affected by mechanical, electrical, or other influences that could reduce its reliability.
The laws of kinematics are consistant and repeatable. Therefore, if the instrument indicates that adequate acceleration of the aircraft has been up to the required amount during takeoff roll, then the pilot knows that the aircraft will attain takeoff speed in the shortest possible distance.
The operational use of this instrument is as follows:
As long as the liquid in the transparent tube stays above the ABORT index, continue the takeoff. If the top of the liquid moves below the ABORT index, abort the takeoff.
It should be clear at this point that an aircraft takeoff and abort linear acceleration measuring and indicating instrument has been provided which does not have moving parts that can malfunction, which is simple to build, which requires minimum maintenance, which is unbelievably reliable, easy to read and which occupies a minimum of space on the instrument panel.
It should be clear, however, that the present invention is not to be construed as limited to the forms shown, which are to be considered illustrative rather than restrictive.